<div class="contain">
  <div class="column"></div>
  <div class="column"></div>
  <div class="column"></div>
</div>
<style>
  .column:nth-of-type(1),
  .column:nth-of-type(2) {
    float: left;
    width: 100px;
    height: 300px;
    background-color: green;
  }

  .column:nth-of-type(2) {
    float: right;
  }

  .column:nth-of-type(3) {
    overflow: hidden; /*创建bfc*/
    height: 300px;
    background-color: red;
  }
</style>
